Such apparatus may be used, in particular, in the lubrication circuit of a vacuum pump having vanes and oil seals, in which circuit the lubricating oil is mixed with air so as to obtain a more elastic fluid avoiding knocking during the compression stages of the pump, and thereby reducing the operating noise thereof.
Such lubrication circuits are often equipped with a chemical or mechanical filter device through which the lubrication mixture passes via neutralizing and filter components. During the passage of the mixture, the speed of the stream is reduced, thereby giving rise to at least partial degassing of the oil. In currently-used filter devices, a pocket of air under pressure forms above the oil level, which pocket firstly reduces the effectiveness of the filter by making a portion of the filter component inactive, and secondly produces a heterogeneous stream of air and oil. The volume of the air pocket increases until the pocket reaches the level of the side outlet orifice through which the stream flows out. By then expanding inside the outlet duct, the air fills the outlet duct and creates a flow of air which alternates with the flow of oil. This causes the vacuum pump to operate irregularly, and produces noise.
An object of the invention is to remedy these drawbacks, and to provide apparatus producing a homogeneous flow of gas/liquid mixture at a regular flow-rate.